Low viscosity gear oil composition providing enhanced fuel efficiency

ABSTRACT

A gear oil composition includes base oil including poly-alpha-olefin (PAO) synthetic oil in 70 to 95% by weight and oil-soluble polyalkylene glycol (OSP) synthetic oil in 5 to 30% by weight based on the weight of the base oil. The gear oil further includes a polyalkyl methacrylate-based Viscosity modifer in 5 to 20 parts by weight, based on 100 parts by weight of the base oil.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims under 35 U.S.C. §119(a) the benefit of priority to Korean Patent Application No. 1 0-201 4-01 77652 filed on Dec. 10, 2014, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a gear oil composition having enhanced fuel efficiency and low viscosity. More particularly, it relates to a gear oil composition having enhanced fuel efficiency and low viscosity formed with base oil, a Viscosity modifer and additives, and capable of enhancing fuel efficiency and durability of vehicles by mixing and using poly-alpha-olefin (PAO) synthetic oil and oil-soluble polyalkylene glycol (OSP) synthetic oil in a specific content ratio as the base oil.

BACKGROUND

In general gear lubrication, engagement of gear is a line contact and large weight and pressure are applied to the gear, and therefore, an extreme pressure property is particularly required for gear oil. In this regard, gear oil has compositional characteristics in that an extreme pressure agent is included, which is different from other lubricants. In addition, for gear oil, viscosity capable of distributing sufficient lubricants to all friction parts, and capable of forming suitable oil films for the pressure, the rate and the temperature is required.

Gear oil has been manufactured using combinations of petroleum-derived base oil, and as a typical example, Chevron Tegra™ gear oil has been manufactured including highly purified petroleum-derived Group III base oil and 20% by weight of greater of a viscosity index improver.

Prior inventions relating to gear oil are as follows. The European Patent Application Laid-Open Publication No. 1,570,035 (Patent Document 1) discloses a technology of manufacturing gear oil having low Brookfield viscosity using base oil having low CCS viscosity. The U.S. Patent Application Laid-Open Publication No. 2005-0133407 (Patent Document 2) discloses a technology of manufacturing gear oil having low Brookfield viscosity from Fischer-Tropsch-derived base oil. The U.S. Patent Application Laid-Open Publication No. 2005-0258078 (Patent Document 3) discloses that a mixture of base oil manufactured from high paraffin wax prepared using Group II or Group III base oil has very low Brookfield viscosity.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY

Embodiments of the present invention have been made in an effort to solve the above-described problems associated with prior art, and inventors of the present invention have found out that fuel efficiency and durability of vehicles are simultaneously enhanced when poly-alpha-olefin (PAO) synthetic oil and oil-soluble polyalkylene glycol (OSP) synthetic oil are mixed and used in a specific content ratio as base oil, and a polyester-based Viscosity modifer and additives are mixed thereto.

Accordingly, an object of certain embodiments of the present invention is to provide a gear oil composition having average kinematic viscosity of 7 to 11 cSt at 100° C., average kinematic viscosity of 30 to 60 cSt at 40° C., and having low viscosity of average absolute viscosity of 10,000 to 50,000 cP at −40° C., and capable of enhancing fuel efficiency of vehicles by 1 to 2%.

In certain embodiments, the present invention provides a gear oil composition including (A) base oil including poly-alpha-olefin (PAO) synthetic oil in 70 to 95% by weight and oil-soluble polyalkylene glycol (OSP) synthetic oil in 5 to 30% by weight, and, based on 100 parts by weight of the base oil, (B) a polyalkyl methacrylate-based Viscosity modifer in 5 to 20 parts by weight and, in certain embodiments, (C) additives in 3 to 20 parts by weight.

In certain embodiments, the poly-alpha-olefin (PAO) synthetic oil may have an average kinematic viscosity of 3 to 8 cSt at 100° C., a viscosity index of 130 or greater, and a pour point of −50° C. or lower.

In certain embodiments, the oil-soluble polyalkylene glycol (OSP) synthetic oil may have an average kinematic viscosity of 6 to 12 cSt at 100° C., a viscosity index of 140 or greater, and a pour point of −40° C. or lower.

In certain embodiments, the polyalkyl methacrylate-based Viscosity modifer may have a kinematic viscosity of 650 cSt or greater at 100° C.

In certain embodiments, the polyalkyl methacrylate-based Viscosity modifer may have a number average molecular weight range of 300,000 to 400,000, and may have 4 to 10 C₁₂ to C₁₅ polymer chains.

In certain embodiments, the C₁₂ to C₁₅ polymer chains may include alkyl methacrylate in 60 to 80% by weight and 2-ethylhexyl methacrylate in 20 to 40% by weight.

In certain embodiments, the additives may be one or more selected from the group consisting of a dithiophosphate-based abrasion resistant agent, a calcium-based detergent and dispersant, a phosphate ester-based friction modifier, a bis-succinimide-type ashless dispersant, a polysulfide-based extreme pressure agent, and an anti-oxidant.

In certain embodiments, the gear oil composition may have an average kinematic viscosity of 7 to 11 cSt at 100° C., an average kinematic viscosity of 30 to 60 cSt at 40° C., and an average absolute viscosity of 10,000 to 50,000 cP at −40° C.

Other aspects and preferred embodiments of the invention are discussed infra.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

DETAILED DESCRIPTION

Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

A gear oil composition according to the present invention includes (A) base oil, (B) a Viscosity modifer and, in certain embodiments, (C) additives.

Each constituent forming the gear oil composition of embodiments of the present invention is described in more detail as follows.

(A) Base Oil

An embodiment of present invention uses a mixture of poly-alpha-olefin (PAO) synthetic oil and oil-soluble polyalkylene glycol (OSP) synthetic oil as base oil. In certain embodiments, a mixture including PAO in 70 to 95% by weight and OSP in 5 to 30% by weight is used as base oil. In using a mixture of PAO and OSP as base oil, an effect of enhancing fuel efficiency and durability may not be expected when the OSP content is less than the above-mentioned weight ratio, and a problem of additive precipitation may occur when the OSP content is greater than the above-mentioned weight ratio and is excessively used.

In certain embodiments, the poly-alpha-olefin (PAO) synthetic oil used as the base oil in the present invention may have an average kinematic viscosity of 3 to 8 cSt at 100° C., a viscosity index of 130 or greater, and a pour point of −50° C. or lower.

In certain embodiments, the poly-alpha-olefin (PAO) synthetic oil used as the base oil has average kinematic viscosity of 3 to 8 cSt at 100° C., a viscosity index of 130 to 150, and a pour point of −70 to −50° C.

In addition, certain embodiments of the present invention use oil-soluble polyalkylene glycol (OSP) synthetic oil as the base oil. Polyalkylene glycol is a polymer copolymerizing an alkylene oxide such as ethylene oxide (EO), propylene oxide (PO) and butylene oxide (BO), and the oil-soluble polyalkylene glycol (OSP) used in the present invention as the base oil is a polymer copolymerizing butylene oxide, styrene oxide and the like having higher carbon components than ethylene oxide and propylene oxide, and has fluidity by having solubility for oil, which is different from existing polyalkylene glycol. In certain embodiments, theoil-soluble polyalkylene glycol (OSP) synthetic oil may have an average kinematic viscosity of 6 to 12 cSt at 100° C., a viscosity index of 140 or greater, and a pour point of -40° C. or lower. In certain embodiments, the oil-soluble polyalkylene glycol (OSP) synthetic oil has average kinematic viscosity of 6 to 12 cSt at 100° C., a viscosity index of 140 to 160, and a pour point of −60 to −40° C.

In the poly-alpha-olefin (PAO) synthetic oil and the oil-soluble polyalkylene glycol (OSP) synthetic oil used as the base oil in the present invention, when the kinematic viscosity at 100° C. is less than the above-mentioned range, there is a problem in that gear abrasion may increase, and when the kinematic viscosity is greater than the above-mentioned range, a viscosity increase at low temperatures may intensify, which may cause a problem of operability decline at low temperatures and a fuel efficiency decrease.

The gear oil composition of certain embodiments of the present invention may include a mixture of the poly-alpha-olefin (PAO) synthetic oil and the oil-soluble polyalkylene glycol (OSP) synthetic oil in a range of 65 to 90% by weight, and, in certain embodiments, in a range of 75 to 85% by weight as the base oil.

(B) Viscosity modifer

In certain embodiment of the present invention, a Viscosity modifer is included in order to increase viscosity of gear oil, and increase a viscosity index by suppressing a viscosity increase at low temperatures. A polyalkyl methacrylate-based Viscosity modifer may be used as the Viscosity modifer. In certain embodiments, as the polyalkyl methacrylate-based Viscosity modifer, a polymer material having a number average molecular weight ranging from 300,000 to 400,000, and having 4 to 10 C₁₂ to C₁₅ polymer chains may be used. In certain embodiments, the C₁₂ to C₁₅ polymer chain may include alkyl methacrylate in 60 to 80% by weight and 2-ethylhexyl methacrylate in 20 to 40% by weight. In addition, the polyalkyl methacrylate-based Viscosity modifer may have a kinematic viscosity of 650 cSt or greater at 100° C., and, in certain embodiments, may have a kinematic viscosity of 650 to 1000 cSt at 100° C.

The gear oil composition of certain embodiments of the present invention may include the polyalkyl methacrylate-based Viscosity modifer in a range of 5 to 20 parts by weight, and, in certain embodiments, in a range of 10 to 15 parts by weight based on 100 parts by weight of the base oil. When the content of the Viscosity modifer is small, which is less than 5 parts by weight, viscosity may not be suitably increased at room temperature and high temperatures causing an excessive viscosity increase at low temperatures, and when the content is greater than 15 parts by weight, viscosity increases both at high temperatures and low temperatures, and a problem of durability decline may occur due to a viscosity decrease by shear during a durability progress.

(C) Additives

In the gear oil composition of the present invention, additives, which may include additives commonly used in the art, may be properly selected and added as necessary. Additives approved of an API GL-5 grade or SAE J 2360 may be used.

The gear oil composition of the present invention may include additives out of choice, and the amount of the additives used is not particularly limited in the present invention. If the amount is limited nonetheless, the additives may be included in a range of 3 to 20 parts by weight and, in certain embodiments, in a range of 5 to 10 parts by weight based on 100 parts by weight of the base oil.

In certain embodiments, the additives may include a dithiophosphate-based abrasion resistant agent, a calcium-based detergent and dispersant, a phosphate ester-based friction modifier, a bis-succinimide-type ashless dispersant, a polysulfide-based extreme pressure agent, or an anti-oxidant. However, the additives used are not limited to the above examples.

The gear oil composition of certain embodiments of the present invention having constituents and compositions as described above may have an average kinematic viscosity of 7 to 11 cSt at 100° C., and an average kinematic viscosity of 30 to 60 cSt at 40° C. It may have low viscosity. For example, its average absolute viscosity may be 10,000 to 50,000 cP at −40° C. When comparing to high viscosity oil having average kinematic viscosity of 13 to 17 cSt at 100° C., average kinematic viscosity of 60 to 150 cSt at 40° C., and average absolute viscosity of 50,000 to 200,000 at −40° C. used in existing gear oil due to a durability problem, the gear oil composition of the present invention maintains low viscosity, and a result of enhancing fuel efficiency of vehicles by 1 to 2% is obtained.

EXAMPLES

Hereinafter, embodiments of the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Examples 1 to 3 and Comparative Examples 1 to 5.

Gear oil was prepared using constituents and content ratios shown in the following Table 1.

TABLE 1 Gear Oil Composition Example Comparative Example Category 1 2 3 1 2 3 4 5 Base PAO¹⁾ 95 90 70 100  — 97 60 90 Oil OSP²⁾  5 10 30 — 100   3 40 10 (% by Weight) Viscosity 10 10 10 10 10 10 10 30 modifer³⁾ (Parts by Weight)* Additives⁴⁾ (Parts 10 10 10 10 10 10 10 10 by Weight)* ¹⁾Poly-alpha-olefin, PAO4 manufactured by Eneos (kinematic viscosity at 100° C.: 3.9 cSt, viscosity index: 130, pour point: −69° C.) ²⁾Polyalkylene glycol, OSP-32 product manufactured by Dow Chemical Company (kinematic viscosity at 100° C.: 6.5 cSt, viscosity index: 146, pour point: −50° C.) ³⁾Polyalkyl methacrylate, 0-050 manufactured by Evonik Industries ⁴⁾Additive package: Anglamol 6043 manufactured by Lubrizol Corporation (products approved of an API GL-5 grade or SAE J2360) *The content of the Viscosity modifer and the additives is the amount used based on 100 parts by weight of the base oil written in parts by weight

For the gear oil prepared according to Examples 1 to 3 and Comparative Examples 1 to 5, physical properties were measured using the following methods. The results are shown in the following Table 2.

[Physical Property Measurement Method]

(1) Kinematic viscosity measurement method: it was measured using an ASTM D 445 measurement method.

(2) Low temperature viscosity measurement method: it was measured using an ASTM D 2983 measurement method.

(3) FZG gear durability test: it was measured using an FVA No.2/IV measurement method.

(4) Axle delivery efficiency (%) measurement method: a percentage of power input to a transmission and power output from the transmission was measured.

TABLE 2 Target Example Comparative Example Category Value 1 2 3 1 2 3 4 5 Kinematic 100° C. Lower the 7 9 11 6 Precipitation 7 Precipitation 15 Viscosity Better (cSt)  40° C. Lower the 30 45 60 28 — 40 — 130 Better Low −40° C. Lower the 10,000 30,000 50,000 10,000 — 20,000 — 150,000 Temperature Better Viscosity (cP) FZG Gear Limit (gear) Higher 12 12 12 10 — 11 — 12 the Better FZG Gear Durability (hr) Higher 72 72 84 48 — 48 — 60 the Better Axle Efficiency Higher 96 97 97 96 — 96 — 93 the Better In the compositions in Comparative Example 2 and Comparative Example 4, precipitate production was identified, and physical properties were not measured.

As shown from the results in Table 2, durability of Comparative Example 1 including PAO alone as base oil and Comparative Example 3 having low OSP content was low compared to the examples. In addition, precipitation of the additives was observed in Comparative Example 2 including OSP alone and Comparative Example 4 excessively using OSP. Furthermore, in Comparative Example 5, a phenomenon of an excessive kinematic viscosity increase was identified due to the excess Viscosity modifer. As a result, it can be seen that a problem of durability decline or additive precipitation occurs in a gear oil composition outside the bounds of the content ranges proposed in the present invention.

Meanwhile, the gear oil compositions of Examples 1 to 3 had average kinematic viscosity of 7 to 11 cSt at 100° C. and average kinematic viscosity of 30 to 60 cSt at 40° C., and had average absolute viscosity of 10,000 to 50,000 cP at -40° C.

According to the results described above, it was identified that the gear oil composition according to certain embodiments of the present invention had relatively low viscosity, but was capable of securing gear durability, and fuel efficiency was enhanced by 1 to 2%.

Accordingly, the gear oil composition according to the present invention is particularly effective in improving gear fitting/scoring by increasing abrasion resistance of a transmission and an oil film despite having low viscosity, and in enhancing fuel efficiency as well.

The gear oil composition according to certain embodiments of the present invention has average kinematic viscosity of 7 to 11 cSt at 100° C., and average kinematic viscosity of 30 to 60 cSt at 40° C., and average absolute viscosity of 10,000 to 50,000 cP at −40° C.

The gear oil of the present invention having compositional characteristics as above has low viscosity compared to existing gear oil, but has enhanced durability, and is effective in enhancing fuel efficiency by 1 to 2%.

The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 

What is claimed is:
 1. A gear oil composition comprising: base oil including poly-alpha-olefin (PAO) synthetic oil in 70 to 95% by weight and oil-soluble polyalkylene glycol (OSP) synthetic oil in 5 to 30% by weight based on the weight of the base oil; and a polyalkyl methacrylate-based Viscosity modifer in 5 to 20 parts by weight, based on 100 parts by weight of the base oil.
 2. The gear oil composition of claim 1, further comprising: additives in 3 to 20 parts by weight, based on 100 parts by weight of the base oil.
 3. The gear oil composition of claim 1, wherein the poly-alpha-olefin (PAO) synthetic oil has an average kinematic viscosity of 3 to 8 cSt at 100° C., a viscosity index of 130 or greater, and a pour point of −50° C. or lower.
 4. The gear oil composition of claim 1, wherein the oil-soluble polyalkylene glycol (OSP) synthetic oil has an average kinematic viscosity of 6 to 12 cSt at 100° C., a viscosity index of 140 or greater, and a pour point of −40° C. or lower.
 5. The gear oil composition of claim 1, wherein the polyalkyl methacrylate-based Viscosity modifer has a kinematic viscosity of 650 cSt or greater at 100° C.
 6. The gear oil composition of claim 1, wherein the polyalkyl methacrylate-based Viscosity modifer has a number average molecular weight range of 300,000 to 400,000, and has 4 to 10 C₁₂ to C₁₅ polymer chains.
 7. The gear oil composition of claim 6, wherein the C₁₂ to C₁₅ polymer chains include alkyl methacrylate in 60 to 80% by weight and 2-ethylhexyl methacrylate in 20 to 40% by weight.
 8. The gear oil composition of claim 2, wherein the additives are one or more selected from the group consisting of a dithiophosphate-based abrasion resistant agent, a calcium-based detergent and dispersant, a phosphate ester-based friction modifier, a bis-succinimide-type ashless dispersant, a polysulfide-based extreme pressure agent, and an anti-oxidant.
 9. The gear oil composition of claim 1, having an average kinematic viscosity of 7 to 11 cSt at 100° C., an average kinematic viscosity of 30 to 60 cSt at 40° C., and an average absolute viscosity of 10,000 to 50,000 cP at −40° C. 